132 OF UUDS. 



raised from seed in our greenhouses, are of still shorter 

 duration, and can be preserved by cuttings for a few 

 successive seasons only ; yet several of these stand in 

 our botanic works, with all the importance of real spe- 

 cies. Gardeners know bow many of the most hardy 

 perennial herbs require to be frequently renewed from 

 seed to exist in full vigour ; and though others appear, 

 to our confined experience, unlimited in that respect, 

 we have many reasons to believe they are not so. Pro- 

 pagation bv seeds is therefore the only true reproduc- 

 tion of plants, by which each species remains distinct, 

 and all variations are effaced ; for though new varieties 

 may arise among a great number of seedling plants, it 

 does not appear that such varieties owe their peculiari- 

 ties to any that may have existed in the parent plants. 

 How propagation by seed is accomplished will be ex- 

 plained in a future chapter, as well as the causes of some 

 varieties produced by that means. 



Mr. Knight, in the Philosophical Transactions for 

 1805, has shown that buds originate from the alburnum, 

 as might indeed be expected. The trunks and branch- 

 es of trees, and the knobs of genuine tuberous roots, like 

 the potatoc, are studded with them ; in which respect, 

 as Professor Willdenow judiciously observes. Princi- 

 ples of Botany, p. 15, such roots essentially differ from 

 bulbous ones, which last are themselves simple buds, 

 and produce their shoots, as well as their offsets, either 

 from the centre or from the base. 



The contents of buds are different, even in different 

 species of the same genus, as Willows. The buds of 

 some produce leaves only, others flowers ; while in oth- 



